Electret array sensitive to radio waves



Sept. 9, 1952 l R. H. RINES 2,610,245

ELECTRET ARRAY SENSITIVE TO RADIO WAVES Filed Feb. 18, 194e 2 SHEETS- SHEET 1 @y MMM Aiionngy Sept. 9, 1952 R R|NE5 ELECTRET ARRAY SENSITIVE TO RADIO WAVES 2 SHEETS--SHEET 2 Filed Feb. 18, 1946 PULSf ww H M Atonngy Patented Sept. 9, 1952 UNITED STATES I PATENT No1-FICE ELCTRET ARRAY SENSITIVE TO 'RADIO WAVES Robert H. Rines, Brookline, Mass. Application February 18, 1946, Serial No. 648,482

(Cl. FX8-6.8)

Claims.

The present V,invention relatesV to electric systems, and more particularly to radio-receiving systems that, while having more-general fields of usefulness, are especially adapted :for `use in television. f

An object of the invention isrto provide a novel combined radio-and-television system. I

Another object of the present -invention is to provide a new and improved radio-locator system for both detecting the presenceof a body and rendering it visible.

Other and further objects will be explained hereinafter and willbe more particularly pointed out in themappended claims.

The invention Will now be more fully explained in connection with` the accompanying drawings, in which Fig. l is a diagrammatic view of circuits and apparatus arranged and constructed in l accordance with a preferred embodiment thereof; Fig.2 is a view of a modification; Fig. 3

is a diagram showing an airplane object from'v which radio waves are reflected and scattered to the receiving system of Fig. 1; and Fig. 4 is a View of a further modication.

An electromagnetic-Wave generator 4 is shown exciting-a dipole 2 to produce ultra-high-frequency pulsed-radio energy, say, of 3 or 1.5 centimeters Wavelength, .A continuous-wave or any other type of modulated-wave generator may be employed, but pulsed energy, at present, has the advantage of economical and easy high-power ultra-high-frequency generation.

The waves emitted by the dipole 2 maybe 6. The parabolic reflector S is shown directing the -Waves toward an object, say, an airplane 8,-

from which they are reflected and scattered toward a receiving station.`

At the receiving station, the radio waves thus reflected and scattered from the object 8 may be focused byan electromagnetic dielectric lens 5, such as polystyrene, upon a bank or array 'I comprlsing a plurality of normally ineffective radioreceiving pick-up unit antenna elements. The dielectric lens 5 may be replaced by any other type of Well-known lens,A mirror or other directive system for focusing the electromagnetic energy scattered and rellected from the object 8 on the bank orarray l of piek-up elements.

The pick-up elements of the bank or array l are shown arranged in the form of rows and columns, in the proximity of the focal plane of the lens 5. The lrst or uppermost row of the bank is illus- I 2 second row from the top is shown comprising the sections I8, 20, 22, etc. The thirdl or next-lower row is shown comprising the sections 24, 26, etc., vand so on vfor the remaining rows of pick-up elements; Though-only a small number of pickup units is shown in each row, this is merely for illustrative purposes, in order not to confuse the disclosure. It will be understood that, in practice, a large number of pick-up units will be employed in each row, say, 180.

The sections I8, I8, 24, etc., are arranged in the rst or right-hand column. The sectionsH, 20, 26, etc., are disposed in the second column from the right. The sections I4, 22, etc., are disposed in the third column from the right, and so on. There may be as many columns as there are pick-up units in each row. Though each column is shown as comprising only a few pick-up units, this is again in order not to complicate the drawings. l

The pick-up units will, of course, all receive the reflected or scattered radio waves through the lens 5 simultaneously. There will be focused on each pick-up unit a radio-frequency voltage corresponding to the scattering from a corresponding view of the object 8. The pick-up elements will thus receive different eld strengths of radio energy, corresponding to the amount of energy reflected or scattered from the various parts of the object 8 and converged upon the array l of pick-up elements by the lens 5. A radio-energy picture of the object 8, as will presently be explained, is thus recorded upon the array, specic elemental areas of which will correspond to specific elemental areas of the object 8. By means of the present invention, this radio-energy picture may be converted into a visible picture |23. Aecordngto the preferred embodiment of the of a. display cathode-ray oscilloscope tube 90.

Though the tube 9U, and also the hereinafter-V described cathode-ray oscilloscope-like member 89, are shown operating on the electrostatic prinetc., shown as equally spaced horizontally. The

ciple, magnetic deflection or a combination of magnetic and electrostatic forces may be employed. The invention provides a means for producing upon the screen Ille` images corresponding to the radio-frequency energy received by the pick-up elements.

Provision is made for rst vrendering the normally ineffective pick-up units ID, I2, I4, IIB, etc., of the lirst row successively effective momentarily in the display circuits; for then rendering the pick-up units I8, 26, 22, etc., of the second row Each electret will absorb and rectify the radioand the charge of theelectret. 'Ihis changewill result both as a consequence of the absorption and of the rectifying action by the electrets of the radio-frequency energy received by the electret electrodes. As the electron stream successvelyimpinges upon the successively disposed `electrets, during the scanning, it successively discharges them. This produces a corresponding change in the inputvoltage to the amplifier 19, indicative of the radio-frequency energy im.- pingedon'the respectiveelectrodes. I

The electron stream will instantaneously discharge each differently-charged and diierentlypotentialed electret to give an indication in the load 58 and the amplier 19, or it will give rise .to a change in the electron-beam current when it impinges upon the variously resistive electret elements, or therermay be a combination of these 1 ticular element ofthe mosaic 1 willbe dependent upon the value of the series resistance o-f the electret. As before explained, this resistance is a function of the impinged radio-frequency energy.

As the stream scans the successive elements ||0, H2, etc., therefore, the signal across the load 58 varies in accordance with the value of the resist- `ance of the successive electrets which manifests itself in the input circuit of the amplifier 19.

`Mosaics of electrets for the member |39 may also take the form of Fig. 2, where electrets 8|, 84. 8|?, 88 are provided with front electrodes |8I, |84, |86, |88 exposed to the radio energy converged by the lens 5. The electrode strips V| 8|, |84, |86, |88 may be of length one-quarter of the wave-lengthl of the radio waves. The other electrodes 28|, 284,286, 288 may be in thein'- terior of the tube 89. The electrode strip 18|, |84, |86, |88, etc. may face the electron stream,

`and may be scanned by it. The electrodes 28|,

'284, 286, 280 will be capacitively coupledtothe front electrodesand will assume the homocharge `of the electret.` Thus, the electron streamlwill impinge on surfaces of different charge or potential, and the scanning will take place according `to the principles previously described.

vThe electrets may be separated fromadjacent electrets by dielectric material 200.

As the electron stream produced from the cathode 95, in response to appropriate horizontalsweep-time-base voltages applied to the verticallydisposed deiiector plates 99. and ofthe cathode-ray-tube-like member Y89, travels across the pick-up elements in the disc 9, they will seccessively discharge into a grounded'preferably 'linear amplifier 19, by way of a conductor 18. If desired, the amplifier 19 may be replaced by a bank` of linear amplifiers, one corresponding to each of the pick-up elements.

The output of the amplifier 19 will obviously vary, at successive instants, in accordance with the radio-frequency energy received by the successive corresponding pick-up elements.

A pulse generator, which may, if desired, be the same pulse generator 4, may be employed to trigger a horizontal-time-base-sweep circuit V63 `and 6 a vertical-sweep circuit 69, according toconventional and well-known television technique. The pulse generator 4 may feed, through an attenuator andre'ctier to an oscillator or any similar or` equivalent television cir-cuit. One such circuit is shown as a pulse-recurrence-frequency multiplier 65, for applying many pulsesfcorresponding to-each radio-'frequency pulse for the period between successive radio pulses. to trigger the horizontal-sweep circuit 63. The horizontal- `time-base sweep will thereby be produced between the vertically disposed deector plates 99 and |0|, occurring as Vmany times, saybetween successive radio-frequency transmissions, as thereare rows of pick-up antennas. The pulse generator 4' may also feed, through `the attenuatorand rectifier to trigger the vertical-sweep circuit 69, once corresponding vto every radio-frequency "transmission One vertical' sweep .will then occur between the horizontally disposed rplates |03, |05 during the periods between successive radio-pulse transmissions, corresponding to as many horizontal sweeps as thereare :rows of antennas, causing each of .the horizontal fvertical sweep corresponding to as many horizontal` sweeps from the horizontal-sweep circuit .63 as there are rows of pick-up units.

AMeans` is providedv for producing upon theA screen |06 of the display oscilloscope 90, images corresponding to the radio-frequency energy received by the corresponding pick-up mosaic antenna elements; The screen |06 -is illuminated by an electronstream in the oscilloscope'90. This Aelectron stream is` synchronized4v to travel with' the electron stream of the cathode-ray-like `member 89, The horizontal-sweep circuit 63 is connected to the horizontal-deflector plate |00 of the oscilloscope by a conductor 61, and to the `hori'zontal-delector plate 0| of the oscilloscopelikemember 89 by the conductor 61 and a conductor |34. The vertcal-sweepcircuit 69` is connectedto the vertical-deflector plate |02 of the oscilloscope 90 by a conductor 1|, and to the ver- -tical-deflectorplate |03 of theoscilloscope-like the action o f the amplier 19, topass by the grid 92, to the anode at of the oscilloscope tube 90. The electronswill continue to `travel Vinrfjla .stream from the anode 95, between the pair4 of vertically disposed oscilloscope deflector plates 98 and` |80, of which the plate 98 is shown grounded, and between Ythe pair of horizontally disposed `oscilloscope deiiector plates .I 02 and |04, of which the plate |04 is showngrounded,

, possible;`

` 'largenyoltageswill b-e'ap'plied to the-horizontally dispesede deflectorplates. |02, ,|04 and .l0-33,105, respectivelmfbyithe vertical-sweep circuit. vAfter `,t'heplast suchhorizontalfsweep, the voltagel be:-

tween. the horizontally disposed plates |02, -I04 y"nenthorizontalsvveeptherefore, will start again ,ais-iiftlieiirstscntopirow.:l l Successivelydisposedareasrof,*the*screen 10S 'of `tlieaoscilloscope,I trwillstherefore correspondpzto Y =the1-siinilarlydisposedmosaicLantenna sectionsin theadisca of themember 89.. L Each-:spot: .along a particular '.horizontalf sweep, i therefore," iwillirbe- 'come'brightenedon the screen i D6A according to the: amount ofzradio' ',energyf received rby the. cor;- -responding pickJ-:up A`element, `and fed,A by Wayzof the-amplifier 79,:t`o the control "electrode, 32Y ofv the cathode'ray. oscilloscope 902.-'. 'i i, f

i *Armore sensitivel video ',signalrdevice: ,n1ight.v be Yanya )well-.known bridgeaidetector: offs. say, Vthe Wheatstone construction. Ifrlfthe'electrets :are connectedinia directlcurrentseries circuit, then thefba-nk 'or condenserzelectrets may serve .asazan extremely sensitive radio-detecting element 'of' a .-wlieatstonepzbridge.. inrwhi'ch l,they :may I be' ibalanc'edagainst xed impedance elements' 2:12-, 42M fand-Z'tas shown in'Fig. 4u' The short-circuit.- ing of each successive electret bythe' electron stream, .diagrammatically shown. as r'shorting switches 205, 201, 209, in parallel withk the 'elecr- 'trets .2041,1'206, 208, would thus'be'markedlyindicated `inthe amplifier 19 and fed to the control electrode v92 ofA the display oscilloscope 90.V

Although the invention' has Vbeen described `in 'connection-with mosaic-antennas arranged in rows' and columns, it will be understood that this isnot'essential', for other arrangements are also Antennas arranged along concentric circles covering the eld, or a continuous spiral, -willialsov serve, though the'oscilloscope arrange'- iment Would, of course, be ,correspondingly modi- Aed-l In thecase of the concentric circles and the spi-ral', theantennas would be rendered effective in1tWo'-'dimensional order, asin the case of the rows andv columns before described. The an- @Further modifications Will' occur to persons skilled .in the art, and all such arev considered toV vfallwwithin the spirit and scope of the invention, asiidelisnedin the appended claims. What is claimed is: "1;" An electric system having, inV combination, afplurality of'successively disposed rac'lio-receiv-` in'gelements for receiving radio Waves, each elementincluding an electret comprising a polarized ,dielectric base in combination with radio-.Wave absorbing material provided on one side With an electrode Y tuned to the frequency of the radio wavesv and connected on another side to a commonlload Acircuitmeans for focusing a radiolWavre image of an object upon the radio-receiving elements, vmeans for producing a iirst electron stream for impinging on the elements, means for V causing the first electron stream to scan the successive elements ofthe plurality, of elements, an oscilloscope havinga screen and means for producing a secondelectron stream impinging' cn the screen, means for causing the second electron strea'mait'o scan the-` successivenertionsfiof the Yscreen.-r incsynchronismfwithi thefscarming;

by the ,'iirstrnarnedf, scanning L- meansfand means connected tothei` common :load circuit :controlled by 'the rst electrenrstream` and responsive vto the radio; energy received; by the success-ive radioelements for 'receiving radio :Wai/fes, .each `element including an electretycomprising;'axpolaxizedfdielectricfbase combined with. a-radowavesabsorb- K ing; material providedi` 'on l. {cnaf-emey with :means connected' 'on .another sideto .a fcommon: load-ciricuit;r means; `for focusing; a ',radio-,vvavefimage 'of means :for scanning 'the Asuccessive 'elements-:0f

the plurality of elements, display means',and means connected-to the common loadci'rcuit con-V trol-ledL bythe scanningzmeans and responsive to thefradio `energy.r-eczeived :by-the successive radios receivingelementsi for" controllingv Athe'ldisplay means duringxthe scanning processtosproduce a likeness of thecbject Lupon the :display` means, e x

3. An electric system having, in 'combination-',--A a I pluralityv off successively disposedn radioereceiiring elements forreceiving radio Waves, each element including ian.v electret comprising a polarized; di:- electric base gincombination withuraniumv` oxide provided on one side with means tuned to-ithe fre-l lquency ofg'theradiorwaves andnconnectedzen. alli Vother: side to ra' Lccmmoni loadY` "circuit, mea-nslfor Y receivedjbythe-msuccessive radio-receiving--ele'- Y imentslioncontrolling thedisplay means during the-,scanning process rrtogproduce fa, likeness of the vob'ject-uponsthe'f lismlay. means.' j g 'T f 4. electric system having, :inecoinbination,` a

`plurality of. successively disposed radio-receiving ,elementsxfor receiving radio`v Waves; each element including; an'electret comprising a polarized-dife electric base in .combination ivithfsiliconlprovided ononevside With'means tun-ed to theffrequency of ftheradio waves and connectedon'anotheri side t toa common. load circuit, means-for focusingza radio-Wavel imageofan Voba'ect upon Athe radioreceivi-ng elements,l meansor scanningtheu successive elementsof thev plurality'of elements,:dis. play means', and means connected .to the common load. circuit controlled by f the scanning fmeans and .responsive to-"the radiorenergy receivedrby' the successive radio-receiving elements `for 'controlling' `the display 'niea'ns during the scanning process Vtoaproduce a'likenessf of the ob-jectrupon the: display means.l

' 5.= Anfelectricsystern having, lin combinatioma Vand connected on-another side to 1a common load circuit,n means'fo'r focusing va ra'dio-waveimage of" an' obj ecty upon the:V radio -receivi-ng elements, means for producing a. rst" electron stream for xthe successive elements.'.oifI they plurality lc'eiements j impinging on the elements, means for causing the rst electron stream to scan the successive elements of the plurality of elements, an oscilloscope having a screen and means for producing a second electron stream impinging on the screen, means for causing the second electron stream to scan the successive portions of the screen in synchronism with the scanning of the successive elements of the plurality of elements by the rstnamed scanning means, and means connected to the common load circuit controlled by the rst electron stream and responsive to the radio energy received by the successive radio-receiving elements for modulating the second electron stream during its scanning process to produce a likeness of the obj ect upon the screen.

ROBERT H. RINES.

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